Various industrial processes often require mixing of liquids that involve ratios as low as one part in five thousand (1:5000). Even lower mixing ratios, below 1:10,000, can be involved in specialized cases. Currently, such mixing is attained using sophisticated diaphragm pumps and electronic logic. Such pumps are difficult to operate and are quite expensive. For example, a commonly used, low volume, high pressure gas chromatography pump costs approximately $5000 per unit.
Moreover, current systems require electrical power for operation. The existing systems utilize high cost electronic control logic for the electric metering pumps, mixing chambers and fail safe systems. The electronic logic, pumps and fail safe parts can cost from about $4000 up to about $12,000. These costs can double if an electronic pump must be made explosion proof.
There are some non-electric pumps available for attaining low ratio proportioning. Such pumps generally deliver ratios as low as one part in four thousand (1:4000). This 1:4,000 ratio is achieved in conventional pumps at the lower end of their adjustment window and has proven unreliable in the field.
The metering process becomes even more complicated when the mixing of two concentrates is required before the mixture is proportioned with a third liquid at a low ratio. One such system available to mix two chemicals utilizes two water-actuated pumps in series, but the system is subject to a host of problems due to the water hammer effect which occurs with the arrangement. Furthermore, additional water motors must be utilized to make the system function, thereby adding to the cost and complexity.
There is no available, non-electric system that will automatically perform this process, especially if the water flow-rate is as low as one fluid ounce per minute. Accordingly, it would be desirable to have available a fluid powered proportioning system that can accurately achieve low ratio proportioning.